Cosmic collision is caught on cam

Space scientists have snapped a spectacular cosmic pile-up – a collision involving four galaxies and many billions of stars. The crash scene lies 280 million light years from Earth in the constellation of Pegasus, the winged horse.

It is labelled Stephan’s Quintet because a fifth galaxy is visible in the foreground and not involved in the collision.

Astronomers created the picture using a combination of images taken with NASA’s Chandra X-ray observatory in space and the giant Canada-France-Hawaii Telescope on Hawaii.

One galaxy in the new picture, NGC 7318b, is passing through the others at almost two million miles per hour, causing a huge shockwave that shows up as the central bright blue ridge. The others are called NGC 7317, NGC 7318a, NGC 7318b and NGC 7319.

Despite the collision, the many billions of individual stars are unlikely to run into each other due to the vast distances between them. But the pull of the galaxies on each other have produced the long bright tails visible in the picture.

Chandra scientists say the Quintet has also probably been heated by supernova explosions and space breezes from the stars like our own solar wind. There is evidence, too, for previous collisions within the group of galaxies, in the shape of a larger halo of X-ray emission that is not visible in this picture but was detected by the European Space Agency’s XMM-Newton satellite.

Cosmologists are interested in Stephan’s Quintet because it gives them a rare opportunity to observe a group of “star cities” as it evolves from spiral galaxies to ellipticals.